Most research on the prevention of osteoporosis has been derived from older women. Prevalence is much higher in women than in men due to lower body mass, longer life span, and a precipitous decrease in sex hormones at menopause. However, osteoporosis is a growing concern for men as well as they are now commonly living beyond the age of 75 when hip fracture incidence rates begin to rise exponentially. Diet is recognized to be an important component of osteoporosis prevention, yet dietary factors that have been examined in women are typically applied to men without sufficient study to determine how these factors may differ by gender. Even in women, dietary factors that have been studied for some time, such as calcium, remain controversial as to the magnitude of their effect. The investigators on this proposal intend to study diet in relation to the risk of hip fractures due to low or moderate trauma over a twenty-year period in over 45,000 men in the Health Professionals Follow-up Study. The dietary factors to be studied in detail include nutrient intakes of calcium, vitamin D, retinol, and vitamin K, and food consumption of milk, dairy, fruits, and vegetables. These same investigators have already examined these dietary factors in relation to risk of hip fracture in women in the Nurses'Health Study using the same dietary instrument, the same follow-up procedures for ascertaining incident fractures, and the same biennial assessment of non-dietary risk factors, including body weight, smoking, and physical activity. This will allow for gender comparisons of the influence of diet on risk of hip fracture. Clearly, more research is needed on osteoporosis that focuses solely on men. Better knowledge of dietary factors could add greatly to advice that is currently given to men for the prevention of osteoporotic hip fractures. PUBLIC HEALTH RELEVANCE: Most of the previous research on diet and osteoporosis has focused on women, and gender differences have not been adequately examined. In this proposed research, dietary influences on risk of hip fracture will be examined in a cohort of men and results will be compared with those from a companion cohort of women. Results from this research would contribute to dietary advice for prevention of osteoporosis that is specific for men and would encourage expansion of public health messages beyond the current audience of postmenopausal women.